Why do skylights and chimneys leak first?
Shingles shed water downhill in overlapping rows. A chimney or a skylight interrupts those rows. Flashing is the set of overlapping pieces that carries water around the obstacle and back onto the shingles below. It works by lapping, not by caulk. Where someone has leaned on caulk or roof cement, the clock is running, because sealant dries and cracks after a few years of sun and frost.
How does chimney flashing work?
A chimney is flashed with four parts. An apron covers the downhill face. Step flashing climbs each side, one piece woven into every course of shingles. Counter flashing is set into a mortar joint and laps down over the step flashing. Behind a wide chimney sits a cricket, a small peaked saddle that splits the water so it cannot pool. Building code calls for a cricket when the chimney is more than 30 inches wide.
Stow's 1960s ranches often have one brick chimney. After sixty winters the mortar joints that hold the counter flashing can open up, and step flashing from an earlier re-roof may have been reused. On many 1970s and 1980s houses the chimney is a framed chase with siding on an outside wall, and the weak point is the top corner where the chase meets the roof.
Signs to look for: a stain on the ceiling near the fireplace, damp wood in the attic beside the chimney, rust lines on the flashing, or tar smeared along the joint.
Can a leaking skylight be fixed, or should it be replaced?
That depends on where the water gets in. If it enters around the frame, the flashing has failed and the skylight itself may be fine. If the glass is fogged between the panes, or water drips from the glass seal, the unit is finished. A skylight put in when a 1980s or 1990s Stow house was built is now 30 to 40 years old, and its seals were not made for that span.
Condensation can fool you. In winter, warm bathroom or kitchen air meets cold glass and drips. That is not a roof leak. The owner works out which one you have before pricing anything.
The best time to replace a skylight is during a roof replacement. The shingles are already off, the new flashing kit weaves in with the new courses, and nobody opens the roof twice. A skylight that outlives one roof rarely outlives two.
What does reflashing involve?
- The shingles around the opening are lifted or removed.
- Old flashing and sealant come out, and the deck beneath is checked for rot.
- Ice and water shield is wrapped around the opening and turned up the curb or the masonry.
- New step flashing goes in, one piece per course, with a new apron. On a chimney, new counter flashing is cut into the mortar joint. On a skylight, the maker's flashing kit is used.
- Shingles are relaid and sealed, and the finished joint is photographed.
What does a Stow winter do to flashing?
Snow drifts against the uphill side of a chimney or skylight and sits there. In the secondary snowbelt that can last for weeks. Meltwater pools behind the obstacle and tests every lap. The city's own permit guide classes local weathering as severe, and flashing is where severe weathering shows up first.
How do you get skylight or chimney flashing looked at in Stow?
Call (330) 969-6096. The owner inspects it himself, sends a photo report the same day, and gives a fixed written price before any work starts. If the photos show the whole roof is near the end, the report says so, and the flashing can be done with the new roof.
Related pages: roof repair in Stow for pipe boots and nail pops, the free Stow roof inspection, and asphalt shingle roof replacement in Stow.
Stop a flashing leak before winter
A stain by the chimney or a drip from the skylight frame is worth a look now, while the roof is dry.